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SubjectRe: [PATCH v2 3/6] ARM: trusted_foundations: do not use naked function
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On 25.03.2018 21:09, Stefan Agner wrote:
> As documented in GCC naked functions should only use Basic asm
> syntax. The Extended asm or mixture of Basic asm and "C" code is
> not guaranteed. Currently this works because it was hard coded
> to follow and check GCC behavior for arguments and register
> placement.
>
> Furthermore with clang using parameters in Extended asm in a
> naked function is not supported:
> arch/arm/firmware/trusted_foundations.c:47:10: error: parameter
> references not allowed in naked functions
> : "r" (type), "r" (arg1), "r" (arg2)
> ^
>
> Use a regular function to be more portable. This aligns also with
> the other smc call implementations e.g. in qcom_scm-32.c and
> bcm_kona_smc.c.
>
> Cc: Dmitry Osipenko <digetx@gmail.com>
> Cc: Stephen Warren <swarren@nvidia.com>
> Cc: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
> Changes in v2:
> - Keep stmfd/ldmfd to avoid potential ABI issues
>
> arch/arm/firmware/trusted_foundations.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/firmware/trusted_foundations.c b/arch/arm/firmware/trusted_foundations.c
> index 3fb1b5a1dce9..689e6565abfc 100644
> --- a/arch/arm/firmware/trusted_foundations.c
> +++ b/arch/arm/firmware/trusted_foundations.c
> @@ -31,21 +31,25 @@
>
> static unsigned long cpu_boot_addr;
>
> -static void __naked tf_generic_smc(u32 type, u32 arg1, u32 arg2)
> +static void tf_generic_smc(u32 type, u32 arg1, u32 arg2)
> {
> + register u32 r0 asm("r0") = type;
> + register u32 r1 asm("r1") = arg1;
> + register u32 r2 asm("r2") = arg2;
> +
> asm volatile(
> ".arch_extension sec\n\t"
> - "stmfd sp!, {r4 - r11, lr}\n\t"
> + "stmfd sp!, {r4 - r11}\n\t"
> __asmeq("%0", "r0")
> __asmeq("%1", "r1")
> __asmeq("%2", "r2")
> "mov r3, #0\n\t"
> "mov r4, #0\n\t"
> "smc #0\n\t"
> - "ldmfd sp!, {r4 - r11, pc}"
> + "ldmfd sp!, {r4 - r11}\n\t"
> :
> - : "r" (type), "r" (arg1), "r" (arg2)
> - : "memory");
> + : "r" (r0), "r" (r1), "r" (r2)
> + : "memory", "r3", "r12", "lr");

Although seems "lr" won't be affected by SMC invocation because it should be
banked and hence could be omitted entirely from the code. Maybe somebody could
confirm this.

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